1. Field of the Invention
The invention relates to the field of environmental measurement technology. It relates, in particular, to a method for measuring the concentration of particles present in a gas, in which method the gas with the particles is guided in the form of a gas stream past a UV light source, the particles are ionized by the UV radiation from the UV light source, the ionized particles are filtered out of the gas stream and the ionic current which arises is measured.
It furthermore relates to a device for measuring the concentration of particles present in a gas, comprising
(a) a tubular measuring chamber through which the gas with the particles flows in the form of a gas stream; PA0 (b) at the start of the measuring chamber a UV light source, past which the gas flows, the particles present in the gas being at least partially ionized; PA0 (c) downstream of the UV light source, an electrically conducting ion filter which filters the ionized particles out of the gas stream and releases the electric charges picked up in the process in the form of an electric current to a downstream electronic measuring unit; and PA0 (d) means for producing the flow of the gas through the measuring chamber. PA0 (e) the means comprise at least one heat source, which is in thermal contact with the gas and induces thermal convection in the gas by heating the gas. PA0 (a) the UV light source is surrounded by a radiation absorber which at least partially absorbs the radiation emanating from the UV light source; and PA0 (b) the radiation absorber is arranged on the measuring chamber, in thermal contact with the gas.
A method of this kind and a device of this kind are disclosed, for example, in U.S. Pat. No. 4,837,440 and an article by H. Burtscher, Bulletin SEV/VSE 80 (1989) 23, 2nd December, pages 1515-1519.